JPH0384515A - Oblique projection type display device - Google Patents

Abstract

PURPOSE:To realize oblique projection while an angle between the normal of a screen and the optical axis of a projection lens is made large by interposing a trapezoid distortion generation optical system between the projection lens and a transmission or reflection type display device. CONSTITUTION:The translucent type or reflection type display device 12 which adjusts the quantity of luminous flux at every picture element is arranged at a proper angle from the vertical to the optical axis 14 of a trapezoid distortion generating lens 13, and then a real image which is given the trapezoid distortion of the translucent or reflection type display device 12 is formed on a back projection type screen 15. Thus, the trapezoid distortion generation optical system is used to increase the angle between the normal of the final projection screen and the optical axis of the projection lens without forming the translucent or reflection type display device in a trapezoid shape previously.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an oblique projection display device using a transmissive or reflective display device such as a liquid crystal display device.

[Prior Art] As shown in FIG. 5, an oblique projection display device using a conventional transmission type or reflection type display device uses a projection lens 51 with a sufficient margin for the image circle. The center 53 of the reflective display device 52 and the projection lens 5
By shifting the optical axis 54 of 1, oblique projection was realized.

In addition, when setting the angle between the normal 61 of the projection screen and the optical axis 63 of the projection lens 62 to be larger, as shown in FIG. A known method is to appropriately set the angle formed by the normal line 65 of the transmissive or reflective display device a64, and to manufacture the transmissive or reflective display device a64 so as to have a trapezoidal shape in advance.

[Problems to be Solved by the Invention] However, such conventional oblique projection display devices had the following problems.

The method shown in Figure 5, which allows diagonal projection without causing keystone distortion, can be used without any problems by shifting the optical axis of the projection lens with ample image circle and the center of the reflective or projection display device. The maximum possible limit is for vertical projection.
The angle is approximately ±15°, and in the case of forward projection, the projection type display device may be placed between the viewer and the projection screen, which greatly impedes viewing. Alternatively, there are cases where a viewer is placed between the projection display device and the projection screen, and there is also the problem that the viewer's shadow appears on the projection screen.

The projection lens of such an oblique projection type display device requires a large aperture lens because it requires a margin in the image circle, and the number of lenses is increased to eliminate aberrations, making it very expensive and large-sized projection lens. This had the problem of becoming a lens.

In addition, in a rear projection type display device, in order to reduce the depth of the device, especially when increasing the screen size, an oblique projection system having an angle of nearly 60' with respect to vertical projection is required. To do this, as shown in Figure 6, the angle formed between the optical axis of the projection lens and the normal line of the transmissive or reflective display device is determined appropriately, and the transmissive or reflective display device is manufactured into a trapezoid shape in advance. A method has been proposed, but in this case, it is necessary to continuously change the size of each pixel, making it extremely difficult to control the capacitance of each pixel, and also impractical from a production technology standpoint.

Therefore, in order to solve these conventional problems, the present invention eliminates the need to give trapezoidal distortion to the shape of a projection type or reflection type display device, maintains a conventional rectangular display device, and further adds a projection lens. This enables oblique projection with a large angle between the normal line of the screen and the optical axis of the projection lens without increasing the image circle of the projection lens, that is, without increasing the aperture of the projection lens. The object of the present invention is to realize an ultra-thin projection display device in a rear projection display device without interfering with the viewing of the projection screen by the viewer and the front projection display device.

[Means for Solving the Problems] In order to solve the above problems, the oblique projection type display device of the present invention (1) has at least one light source and at least one transmission type or reflection type display device, and A keystone distortion generating optical system is inserted between the projection lens and the transmission type or reflection type display device in an oblique projection type display device in which the normal line of the screen and the optical axis of the projection lens are not parallel. .

(2) The trapezoidal distortion generating optical system is characterized by using an optical system that forms a real image of a transmissive or reflective display device, and a rear projection screen for the real image area.

(3) The keystone distortion generating optical system is characterized by using a virtual image of a transmissive or reflective display device.

(4) Real image formation (on the rear projection screen used in the center,
Using an array of micro prisms with a pitch equivalent to one quadrant of the solution for a transmissive or reflective display device, we calculate the angle between the total reflection surface of each prism and the optical axis of the trapezoidal distortion generating optical system, and the total reflection of the prism. It is characterized in that the angle formed between the surface and the optical axis of the projection lens is set at -.

(5) On the rear projection screen used for the real one-image imaging section,
Using an array of optical fibers with a pitch corresponding to one quadrant of resolution for a transmissive or reflective display device, one end of each optical fiber is set approximately perpendicular to the optical axis of the trapezoidal distortion optical system, and the other end of the optical fiber is connected to a projection lens. It is characterized by being set substantially perpendicular to the optical axis of.

[Operation] Since the present invention has the above configuration, even if the projection lens projects onto the screen at a large angle,
(For example, the angle formed by the optical axis of the projection lens with respect to the normal line of the screen is about 60")
Final projection [[i (11) By generating trapezoidal distortion on the opposite side so that trapezoidal distortion does not occur, a transmissive or reflective display device can maintain its conventional rectangular shape and achieve oblique projection at a large angle. It can be done.

Here, since the optical axis of the trapezoidal distortion generating optical type and the optical axis of the projection lens do not coincide and have a certain angle, a real image of the trapezoidal distortion fm of the transmissive or reflective display device is formed. If an array of micro prisms corresponding to the resolution t of a transmissive or reflective display device is used for the screen, as shown in FIG. The light beam 32 emitted from the lamp can be deflected into a light beam along the optical axis 33 of the projection lens, and the light beam 32 emitted from the lamp can be used effectively.

Even if you use an optical fiber that has the resolution of a transmissive or reflective display device instead of a micro prism, the light beam incident on one end of the optical fiber will still pass through the optical fiber.
The light beam is deflected along the optical axis of the projection lens, and the same effect as using a micro prism can be obtained.

[Example] Hereinafter, implementation σq of the present invention will be described based on the drawings. In FIG. 1, the luminous flux emitted from the light source 11 is transmitted to a transmissive or reflective display device! A transmissive or reflective display device that adjusts the amount of luminous flux for each pixel by irradiating the i12 is arranged so as to be inclined at an appropriate angle from the vertical with respect to the optical axis 14 of the trapezoidal distortion generating lens 13. Here, the trapezoidal distortion generating lens is a name that expresses its function, and may be the same as a normal projection lens. As a result, a trapezoidally distorted real image of the transmissive or reflective display device 12 is formed on the rear projection screen 15 . The rear projection screen 15 used here is generally expensive, so in particular, the rear projection screen 15 that deflects the direction of the light beam from the optical axis direction of the trapezoidal distortion generating optical system to the optical axis direction of the projection optical system, as described later, is not suitable. Since it is expensive, it is necessary to keep the area as small as possible.

Therefore, it is desirable to suppress the magnification of the trapezoidal distortion generating lens 13 to about 1x. The trapezoidal distorted image formed here is tilted at an appropriate angle from the vertical with respect to the optical axis 17 of the projection lens 16. As a result, the final projected image (a 1
8, an image without trapezoidal distortion can be obtained even though the image is projected obliquely.

Here, when the desired oblique projection angle, final magnification, and final projection distance are determined, the focal length, magnification, and trapezoidal distortion lens 13 are adjusted so as to prevent trapezoidal distortion from occurring in the final projected image 18. Parameters such as the angle between the optical axis 14 and the projection type or reflection type display device 12 can be appropriately selected.

In addition, in the trapezoidal distortion generating optical system, the real f phenomenon is expressed as f! j! Even if the trapezoidal distortion generating lens 21 is not
A similar effect can be obtained by generating an appropriate trapezoidal distortion using the virtual image 22.

Furthermore, if a micro prism array 31 with a pitch corresponding to the resolution of a projection type or reflection type display as shown in FIG. The resulting light beam 32 can be bent in the direction along the optical axis 33 of the projection lens without waste.

This micro prism row 31 is connected to the optical axis 3 of the trapezoidal distortion generating lens.
In order to turn the light beam 32 along 4 into the light beam 35 along the optical axis 33 of the projection lens, the angle between the optical axis 34 of the trapezoidal distortion generating lens and the total reflection surface 36 of the micro prism 31, and the light beam of the projection lens. A great effect can be obtained by making the angle between the shaft 33 and the total reflection surface 36 of the micro prism 31 negative. It is clear that the micro prism array 31 used here may be continuous in the direction perpendicular to the rough surface shown in FIG. If the total reflection condition does not hold for the total reflection surface of this microprism, it is necessary to arrange a total reflection film of aluminum or the like on the total reflection surface.

Furthermore, if an optical fiber array 41 having a pitch corresponding to the resolution of a projection type or reflection type display as shown in FIG. The emitted light beam 42 can be efficiently deflected in the direction along the optical axis 43 of the projection lens.

Here, a great effect can be obtained by setting one end of the optical fiber 41 substantially perpendicular to the optical axis 44 of the trapezoidal distortion optical system and setting the other end of the optical fiber 41 substantially perpendicular to the optical axis 43 of the projection lens.

[Effects of the Invention] As explained above, the oblique projection display device of the present invention uses a trapezoidal distortion generating optical system, so that the final projection can be achieved without having to make a transmissive or reflective display device into a trapezoidal shape in advance. It is possible to make a large angle between the normal line of the screen and the optical axis of the projection lens, and in the case of a front projection type, this oblique projection type display device will not enter the viewer's field of view or will be in the viewer's shadow. is not projected onto the final projected image. Furthermore, in the case of a rear projection type display device, the depth of the main body can be made significantly thinner than that of a conventional rear projection type display device.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an oblique projection type display device of the present invention. FIG. 2 is an explanatory diagram when a virtual image of a trapezoidal distortion lens is used in the trapezoidal distortion generating optical system of the oblique projection type display device of the present invention. FIG. 3 is a longitudinal cross-sectional view of the rear projection screen of the trapezoidal distortion generating optical system of the oblique projection display device of the present invention, in which a micro prism array is used. FIG. 4 is a longitudinal cross-sectional view of the rear projection screen of the trapezoidal distortion generating optical system of the oblique projection display device of the present invention, in which an array of micro optical fibers is used. FIG. 5 is a longitudinal sectional view of an embodiment of a conventional oblique projection type display device. FIG. 6 is a longitudinal cross-sectional view of an example of a conventional IM of an oblique projection type display device. 11... Light source 12... Transmissive or reflective display device 3 ・ 14 ・ 15 ・ 16 ・ 17 ・ 18 ・ 21 ・ 22 ・ 31 ・ 32 ・ 33 ・ 34 ・ 35 ・ 6 1 2 3 4 . . Trapezoid Distortion generation lens, optical axis of trapezoidal distortion generation lens, rear projection screen, projection lens, optical axis of projection lens, final projection image, trapezoidal distortion generation lens, imaginary (II) by trapezoidal distortion generation lens, micro prism array, from light source Emitted light flux: optical axis of projection lens, optical axis of trapezoidal distortion generation lens, light flux along the optical axis of projection lens, total reflection surface of minute prism, optical fiber array, light flux emitted from light source, projection lens Optical axis of optical axis/trapezoidal distortion Optical axis of optical system 3 4 1 2 3 4 Projection lens transmission type or reflection type display bag center optical axis of projection lens of transmission type or reflection type display bag holder Normal line of projection lens projection The optical axis of the lens is above the normal line of the projection type or reflective display bag projection type or reflective display device.

Claims (5)

[Claims] (1) In an oblique projection display device that has at least one light source and at least one transmission type or reflection type display device, and the normal line of the projection screen and the optical axis of the projection lens are not parallel, the projection lens An oblique projection type display device, characterized in that a trapezoidal distortion generating optical system is inserted between the transmissive type or reflective type display device. (2) A claim characterized in that, in the trapezoidal distortion generating optical system, an optical system that forms an image of the transmissive or reflective display device as a real image, and a rear projection screen for the real image forming section. Item 1. The oblique projection type display device according to item 1. (3) The oblique projection type display device according to claim 1, wherein a virtual image of the transmission type or reflection type display device is used in the trapezoidal distortion generating optical system. (4) For the rear projection screen used in the real image forming section, an array of minute prisms with a pitch corresponding to the resolution of the transmissive or reflective display device is used, and the total reflection surface of each prism and the trapezoidal distortion generating optical 2. The oblique projection type display device according to claim 1, wherein the angle formed by the optical axis of the system and the angle formed by the total reflection surface of the prism and the optical axis of the projection lens are substantially the same. (5) An array of optical fibers with a pitch corresponding to the resolution of the transmissive or reflective display device is used for the rear projection screen used in the real image forming section, and one end of each optical fiber is connected to the optical axis of the trapezoidal distortion optical system. 2. The oblique projection type display device according to claim 1, wherein the optical fiber is set substantially perpendicular to the optical axis of the projection lens, and the other end of the optical fiber is set substantially perpendicular to the optical axis of the projection lens.